In recent years, the physiological function of scarce fatty acid present only at a low ratio in the body has been attracting attention. For example, it has been reported that conjugated fatty acids such as conjugated linoleic acid and the like (non-patent document 1) and ω3 polyvalent unsaturated fatty acids such as eicosapentaenoic acid, docosahexaenoic acid and the like (patent document 1) have lipid metabolism improving effects, diabetes improving effects and the like. There is a high interest in ingesting the aforementioned scarce fatty acid as functional lipids from the diet, and products (foods, etc.) containing them are on the market.
One of the scarce fatty acids is a hydroxylated fatty acid having a hydroxy group in the compound. The physiological functions thereof have not been analyzed sufficiently heretofore due to the absence of a suitable source of supply. Recently, however, a means for highly efficient and highly selective production by an enzymatic reaction using linoleic acid or the like, which is contained in a large amount in vegetable oil, as a starting material has been found (patent document 2). A method of supplying various hydroxylated fatty acids has been secured, along with which studies on the physiological functions thereof have been actively conducted. The present inventors particularly took note of 10-hydroxy-cis-12-octadecenoic acid (HYA) among hydroxylated fatty acids, and reported that HYA has a lipid metabolic abnormality improving effect (patent document 3), an action to enhance intestinal immunity (patent document 4), a suppressive action on intestinal inflammations (non-patent document 2) and the like.
Since it has become easy to obtain high purity HYA as described above, if HYA can be ingested easily, effective utilization of HYA is expected to be promoted by utilizing its physiological functions. However, since the melting point of HYA is about 25° C. (“about” here means ±1° C.) and HYA is solid (or partially liquefied state) at ambient temperature, there was a problem that it is inferior to liquid components in the ease of ingestion and handleability in adding to or mixing with other liquid or solid food components. In addition, the acrid flavor of HYA is an obstacle in ingestion.
On the other hand, a HYA derivative capable of solving the above-mentioned problems has not been reported heretofore.
As regards alkyl ester of HYA, use of methyl 10-hydroxy-cis-12-octadecenoate and ethyl 10-hydroxy-cis-12-octadecenoate as production intermediates for sebacic acid has been reported (patent document 5); however, they have not been utilized for use other than as the production intermediate. In addition, alkyl ester of HYA other than methyl 10-hydroxy-cis-12-octadecenoate and ethyl 10-hydroxy-cis-12-octadecenoate has not been reported to date.